The technical portion of an optician's profession consists in mounting a pair of ophthalmic lenses in or on a frame that has been selected by the wearer, in such a manner that each lens is properly positioned relative to the corresponding eye of the wearer so as to best perform the optical function for which the lens was designed. To do this, it is necessary to perform a certain number of operations.
Once the frame has been selected, the optician must begin by situating the position of the pupil of each eye in the frame of reference of the frame. The optician thus determines mainly two parameters that are associated with the morphology of the wearer, namely the pupillary distance and the height of the pupil relative to the frame.
As for the frame itself, several alternative types of frame are commonly on offer, including a bezel frame, which is the most widespread, a grooved frame having half-rims (of the Nylor® type), and a rimless frame with drilled holes. The present invention relates to frames of the rimless type. This type of frame is becoming very popular because of the contribution it provides in terms of comfort and appearance.
It is also necessary to identify the shape of the lens that is appropriate for the selected frame, and this is generally done using a template or an appliance specially designed to read the inside perimeter of the rim of the frame, or indeed by means of an electronic file prerecorded or supplied by the manufacturer.
Starting from this geometrical input data, it is necessary to cut each lens to shape. Cutting a lens to shape in order to enable it to be mounted in or on a frame selected by the future wearer consists in changing the outline of the lens so as to cause it to match the frame and/or the shape desired for the lens. Cutting to shape comprises edging for shaping the periphery of the lens, and depending on whether the frame is of the rimmed or rimless type with clamping through fastener holes formed at specific points of the lens, it also comprises beveling and/or drilling the lens appropriately. Edging (or cutting to shape proper) consists in eliminating the unwanted peripheral portion of the ophthalmic lens in question so as to change the outline of the lens from its initial shape, which is usually circular, to the arbitrary shape of the rim of the eyeglasses frame concerned, or merely to the shape desired for its appearance when the frame is of the rimless type. This edging operation is usually followed by a chamfering operation that consists in smoothing or trimming the two sharp edges of the edged lens. Usually these operations of edging, chamfering, and beveling are performed in succession on a common cutting out device which is generally constituted by a grinder machine, referred to as an edger, and fitted with a suitable set of grindwheels.
When the frame is of the rimless type, having drilled lenses, the edging of the lens, and possibly the flattening of the sharp edges (chamfering) are followed by appropriate drilling of the lenses for mounting the temples and the bridge for the nose of the rimless frame. Drilling can be performed on the edger providing it is fitted with the corresponding tooling, or it can be performed on a distinct drilling machine. In the context of the present invention, attention is paid in general to the accuracy and to the expense of the various degrees of freedom in movement used for drilling purposes. In addition to this general problem, the invention relates more specifically to drilling performed on the grinder, or more generally on the machine that includes cutting-out means. The machine is then provided not only with cutting-out means, but also with means specifically for drilling.
At present, lenses are usually drilled by manual finishing-off operations. Accuracy thus depends directly on the dexterity of the operator performing the drilling operation.
Recently, partially-automatic drilling devices that are integrated in edger machines have appeared on the market. The contribution of integrating such a function within the machine that performs edging on the lens is manifest, both in terms of operator convenience in performing the operation and in terms of the increase in accuracy procured thereby.
Amongst the technical and economic difficulties that result from this added function, the main difficulty is due to the fact that drilling of quality that is high, as understood in the profession, needs to be performed in such a manner that the axis of the hole that results from the drilling is normal to the tangent at the point of drilling. Installing this orientation function leads to a novel architecture being devised for the machine, given the size of the actuators and encoders that need to be put into place. This difficulty has led certain manufacturers purely and simply to eliminate this function of orienting the drilling axis, which then becomes fixed and parallel to the axis of rotation of the lens. This leads to a function that rapidly presents limits on its suitability for use with lenses that present curvature on the front face.
Concretely, a grinder for edging lenses mainly comprises a frame carrying firstly a machining station that is fitted with one or more edging grindwheels and one or more bevel grindwheels, and possibly chamfering grindwheels, mounted to rotate about an axis under the control of a drive motor, and secondly a carriage that is fitted parallel to the axis of said grindwheels, with two shafts on the same axis for blocking and rotating the lens. These two shafts are mounted to turn about their common axis (which is also the blocking axis) under the control of one or two drive motors and to slide axially relative to each other under the control of another motor. Each of the two shafts possesses a free end facing the free end of the other shaft, and these facing free ends of the two shafts are thus suitable for blocking a lens to be treated by clamping it axially.
The carriage is mounted to move relative to the frame, firstly transversely relative to the axis of the grindwheels, under the control of thrust means urging it along said axis (following a movement referred to as “reproduction”), and secondly axially, parallel to the axis of the grindwheels, under control of suitable control means (often referred to as “transfer” means).
In order to be moved transversely relative to the axis of the grindwheels (reproduction), as is necessary for applying the ophthalmic lens for treatment against the grindwheels so as to reproduce the various radii that the outline of the desired lens is to describe, the carriage may be mounted to pivot parallel to said axis (in which case the carriage is usually referred to as a “rocker”), or else it is mounted to move in translation perpendicularly thereto.
Drilling and/or grooving and/or chamfering modules may optionally be mounted on a moving support for the purposes, where appropriate, of drilling, or grooving the lens after it has been edged.